Samayaluca Dune Field, south of Juarez, Chihuahua Global Climate Change

Climate vs. Weather

Temp Days since Jan 1

Climate System: 5 parts Atmosphere Ocean Cryosphere (ice) Lithosphere Sun and internal earth heating

Climate System Atmosphere –Nitrogen N 2 78% –Oxygen O 2 21% –Argon Ar 0.93% –Carbon dioxide CO % –Other minor gases 0.035%

Ocean influences climate Transfers of heat from tropics to polar regions (i.e., Gulf Stream)

Cryosphere: ICE Melting ice increases ocean volume Sea level was 130 m (425 feet) lower during last ice age (18,000 years ago) Ice reflects solar energy: albedo

What is albedo? Reflectance of land surface Earth reflects about 31% of solar energy

Lithosphere Mountains influence weather Arrangement of continents affects ocean currrents Volcanism affects composition of atmosphere

Solar energy input to Earth’s surface is 342 W/m 2. Heat flowing out of Earth’s deep interior is only 0.06 W/m 2.

Greenhouse Gases CO 2, H 2 0 and methane (CH 4 ): Absorb and re-radiate radiation Insulates and raises Earth temperature

Earth Temperature Normal: 14 o C (57 o F) Without greenhouse gases : -19 o C (-2 o F)

Feedback enhances warming Positive Feedback: –Amplifies changes in the system. –Temperature increase decreases Earth’s albedo by reducing snow and ice cover

Climate Change Understanding Natural Climate Variability: Use the geologic record to understand Earth Climate in the past (Uniformitarianism)

Long-term change can be assessed from ice cores, which record annual cycles of ice formation from snow. * Cycles can be counted back like tree rings to create a long term record. * Ice layers trap atmospheric gas, contain isotopic record of temperature change.

Milankovitch cycles Related to variations in: 1. Eccentricity 2. Tilt of axis 3. Precession (wobble)

High eccentricity increases contrast between summer and winter.

Earth’s tilt axis changes over time

Precession

1941

2004

Columbia glacier

Greenland

What causes sea level rise? Melting ice Hotter oceans are larger volume

Barrier Islands Sea Level Rise

Sea-Level Rise

1 meter rise 2 meter rise 4 meter rise 8 meter rise

GEOLOGIC RESERVOIRS Fossil organic carbon Fossil organic carbon Rock carbonates Rock carbonates Fossil- fuel burning (5.3 Gt/yr) Fossil- fuel burning (5.3 Gt/yr) OCEAN Cement production (0.1 Gt/yr) Land-use change: deforestation, agriculture (1.7 Gt/yr) Land uptake By new plant growth (1.9 Gt/yr) Ocean uptake by air-sea gas exchange (1.9 Gt/yr) Terrestrial biosphere LAND ATMOSPHERE The influence of Carbon on climate change

GEOLOGIC RESERVOIRS Fossil organic carbon Fossil organic carbon Rock carbonates Rock carbonates Fossil- fuel burning (5.3 Gt/yr) Fossil- fuel burning (5.3 Gt/yr) OCEAN Cement production (0.1 Gt/yr) Land-use change: deforestation, agriculture (1.7 Gt/yr) Land uptake By new plant growth (1.9 Gt/yr) Ocean uptake by air-sea gas exchange (1.9 Gt/yr) Terrestrial biosphere LAND ATMOSPHERE Human activities release a total of 7.1 Gt of carbon into the atmosphere each year. New plant growth and air-sea gas exchange remove 3.8 Gt/yr,… …yielding a net atmospheric increase of 3.3 Gt/yr.

Temperature relative to present climate (°C) Thousands of years before present Relative carbon dioxide and methane concentrations High Low Key: Temperature CO 2 Methane There is a decline in both temperature and greenhouse gas concentrations during glacial periods… …and a rapid rise during deglaciation. Climate has been relatively warm and stable during the last 10,000 years.

East Antarctic ice core data Glacial epoch Interglacial epoch

Is Human-induced climate change possible?

Years Temperature CO 2 concentration The 20th-century is clearly anomalous when compared with the last millennium. Northern Hemisphere temperature anomaly (°C) CO 2 concentration (ppm)

Years Temperature CO 2 concentration Global temperature anomaly (°C) A recent warming trend correlates with the increase in CO 2. CO 2 concentration (ppm)

Atmospheric CO 2 Projections Under 3 Alternate Scenarios… Year

….and Estimated Average Surface Temperatures for Those Scenarios Uncertainty envelope due to lack of knowledge of climate system

Global Warming Evidence

Is Global Warming Real? 20 years of data:

Is Global Warming Real? 130 years of data:

Why is Global Warming ignored? Not enough evidence? Better things to spend money on? Cutting emissions will hurt the economy

The EFECTS of climate change might be distant and uncertain The COSTS of curbing greenhouse gases are immediate and substantial!

Global Warming Small steps can reduce carbon emissions These are affordable and multiplied by 100,000,000s of people can be significant

CO 2 is a small part of the atmosphere Small increases have huge effects Greenhouse gases keep earth hot Natural changes in climate occur Recent changes correlate to human activity Changes in lifestyle can avoid catastrophe

Keeling Curve